I have 2 separate ESO accounts. Both experienced various forms of this error. I play exclusively on Windows.
(I notice there was maintenance today, 2021/06/17, on the ESO Store... perhaps my experience is fallout from that? Unfortunately, this is far from the only time I have encountered cryptic failures when trying to buy Crown Packs... in fact, my experience today is somewhat "usual"; I am asking about it finally, because I am tired of the gobbledygook.)
I logged in to one account on www.elderscrollsonline.com, traversed to the store, purchased 2x Crown Packs (21000 variant), paid via PayPal. Both of these transactions worked as expected. When I attempted to purchase the third Crown Pack, upon confirming payment at PayPal, I received an error page presenting me with three options, basically "request a payment update"/"continue"/"try again". None of these options offered any coherent resolution to the issue (just a return to the same error page, or termination of the payment process), and as far as I can tell none of these purchases was processed. This happened repeatedly. After waiting a while (researching online store payment problems and workarounds, see below), I tried again and was able to purchase the 3rd Crown Pack (paid via PayPal).
I logged into my other account on www.elderscrosslonline.com, traversed to the store, purchased 1x Crown Pack (21000 variant), and this time I paid directly with an American Express card. This single transaction worked as expected. When attempting to purchase a second Crown Pack, clicking on the "Buy Now" button on the item's page at www.elderscrollsonline.com routed me directly to an HHTP error page, indicating that server had preemptively closed the connection. This happened repeatedly. After waiting a while (continuing to research online store payment problems and workarounds, see below), I tried again, this time paying with PayPal, and was able to purchase the another 2x Crown Packs.
(As well, as far as I know, there is no way for a customer to purchase multiple items in one transaction. Fewer end-to-end transactions might help work around buggy infrastructure... if that is what this is.)
While the problem was happening, I tried both forms of payment on both ESO accounts, and experienced similar results in all cases. I also logged in both to my PayPal and my American Express "online banking" accounts while this breakage was underway, and saw no indication that either funding source had flagged any kind of attempted fraud (so I don't believe the problems originated with the funding source... in fact I suspect the payment process terminated before either funding source was even contacted). As well, clearly, the same exact purchase process either worked or failed intermittently, seemingly at random and without any coherent error messaging, which I think suggests the problem was not at my end.
(Ultimately, it appears I ended up with the 3x21000 Crown Packs I wanted on each account. I received confirmation emails on each, etc. Once the transactions have time to settle, I will follow up at PayPal and American Express to insure no extraneous charges went through.)
While researching online store problems in the Elder Scrolls Online support knowledge base and finding nothing helpful (all forms of payment information were always correct, worked at least intermittently, and there was absolutely no information on any constraints on multiple purchases that I might have violated, much less any information on what to do about it), I finally decided to submit a ticket. I found the knowledge base article on submitting a ticket. Both the "Submit a Ticket" link and the "Submit a Ticket" button embedded in this knowledge base article generated basically an empty page... containing nothing but a disclaimer regarding "high contact volumes/COVID-19". "My Support" offers access to my ticket history, but no way to submit a new ticket. So, at the moment, I am not certain there is a way to submit a ticket.
All of this seems exceptionally inept to me. The maintenance today might explain things (I can try buying more Crown Packs in a few days, and see if the process is any better). I could also "assume" there are some sort of undocumented constraints on repeat purchases, but I would just be guessing. However, if this guess is in fact valid, perhaps someone should document these constraints, so we can avoid violating them (versus wasting our time chasing our tails)?
On the assumption that Zenimax (or whoever actually supports ESO these days) is really not responsive to problems, even with regard to revenue-generating services like the "Crown Store", I am interested in hearing from the community. Are there any workarounds anyone can suggest? Any sort of black magic or superstition that people believe might wrangle this payment process into something coherent/viable?
Thanks.